The present invention relates to route control of a label switch path of MPLS and GMPLS networks.
Standardization of MPLS (Multi Protocol Label Switching) and GMPLS (Generalized MPLS) is being discussed by the IETF (Internet Engineering Task Force). As signaling protocol which setups a path, there are RSVP-TE (Resource reSerVation Protocol-Traffic Engineering) and CRLDP (Constraint-based Label Distribution Protocol), and they have a structure for explicitly designating the path.
The RSVP-TE uses an object which is called ERO (Explicit Route Object). The ERO is sequentially provided with information about nodes through which it is necessary to pass, and the explicit route is determined according to the sequence. For example, an originating node which starts to generate a path sets the ERO within a label allocation request message and sends it to the next node. The node which has received the label allocation request message further decides the next node according to the ERO. And a path is generated along a route specified by the originating node.
The ERO includes firm designation (also called as the strict designation) which specifies routers which are passed through, vague designation (also called as the loose designation) which does not specify a router to be passed through in a specified section, and also includes their combination. Use of the ERO can control the route of the path (e.g., D. Awduche and five others, “RSVP-TE: Extensions to RSVP for LSP Tunnels”, (pp 23-31), [online], November 2001, RFC 3209, [searched on Mar. 19, 2004], Internet, see <http://www.ietf.org/rfc/rfc3209.txt?number=3209>).
There is technology using the ERO that a network entrance node uses information of the first generated path, to compute the second path to avoid overlapping with the first route. And, when the second path is generated, the network entrance node uses the computed route information to generate the second path in such a manner that it does not overlap with the first path. Thus, there is proposed a recovery method of a protection type using the two generated paths (e.g., JP-A-2002-247084).
As to the failure recovery of the path, there is proposed an object which is called PPRO (Primary Path Route Object) (e.g., J. P. Lang and two others, “RSVP-TE Extensions in support of End-to-End GMPLS-based Recovery (draft-ietf-ccamp-gmpls-recovery-e2e-signalings-03.txt)”, (P 24), [online], February 2004, internet draft, [searched on Mar. 19, 2004], the Internet, see <http://www.ietf.org/internet-drafts/draft-lang-ccamp-gmpls-recovery-e2e-signaling-03.txt>). It describes that route information of the primary path is set on this object and notified to the secondary path.